1. Field of the Invention
The present invention generally relates to a method of forming a gate insulator for a thin film transistor (“TFT”), and more particularly, to a method of forming a gate insulator using oxygen diffusion and a TFT incorporating the same.
2. Description of the Related Art
Gate insulators of thin film transistors (“TFTs”) are dielectric layers formed between gates and channels of TFTs, and are important elements for the proper operation of TFTs. In particular, the thickness of a gate insulator is related to the performance of a TFT. As the thickness of a gate insulator decreases, the capacitance of the TFT increases.
FIGS. 1A and 1B are schematic cross-sectional views illustrating conventional bottom gate type organic TFT structures. Referring to FIG. 1A, a gate 2 is formed on a substrate 1, and a gate insulator 3 is formed over the gate 2 and substrate 1. An organic semiconductor layer 4 is formed on the gate insulator 3 above the gate 2, and a source electrode 5s and a drain electrode 5d are formed on either side of the organic semiconductor layer 4.
Referring to FIG. 1B, a gate 2 is formed on a substrate 1, and a gate insulator 3 is formed over the gate 2 and substrate 1. A source electrode 4s and a drain electrode 4d are formed on the gate insulator 3 so as to be spaced apart from one other, and a semiconductor layer 5 is formed on the gate insulator 3, source electrode 4s and the drain electrode 4d such that lower surfaces of either side of the semiconductor layer 5 contact the source electrode 4s and the drain electrode 4d. 
In conventional organic TFTs having the above-described structures, the gate insulators 3 are generally formed from deposited inorganic or organic dielectric materials, having requisite electrical insulation characteristics and high capacitances. Because organic dielectric materials must be formed so as to have requisite electrical insulation characteristics, they therefore have thicknesses greater than or equal to a predetermined value. On the other hand, since the organic dielectric materials are coated using a spin coating method, gate insulators are formed to be relatively thick. However, as is well known, such thick gate insulators are not suitable for ensuring the desired characteristics of TFTs.
The gate insulators may also be formed from inorganic materials, for both organic and inorganic TFTs. Silicon oxide is a typical example of a material from which such an inorganic gate insulator is formed, such as through a sputtering process or a chemical vapor deposition (“CVD”) process. In view of the above, it would be desirable to provide a novel method of forming a gate insulator for a TFT with desirable dielectric constant and insulating properties.